IBM System/360 System Programmer's Guide

TYPE=J
specifies that, for each data control block referred to, the
programmer has supplied a job file control block (JFCB) to be used
during initialization. A JFCB is an internal representation of
information in a DD control statement.
During initialization of a data control block, its associated JFCB
may be modified with information from the data control block or an
existing data set label or with system control information.
The system always creates a job file control block for
control statement. The job file control block is placed
queue on direct-access storage. Its position, in relation
JFCBs created for the same job step, is noted in a main
table. '
each DD
in a job
to other
storage
When this operand is specified, the user must also supply a DD
control statement. However, the amount of information g~ven in the
DD statement is at the programmer's discretion, because he can
ignore the system-created jot file control block. (See the
examples of the RDJFCB macro-instruction for a technique for
modification of a systen-created JFCB.)
Note: The DD statement must specify at least:
• Device allocation.
• A ddname corresponding to the associated data control block DCBDDNAM
field.
RDJFCB -- Read a Job File Control Block (S)
The RDJFCB macro-instruction causes a job file control block (JFCB)
to be read from the job queue into roain storage for each data control
block specified.
r----------T----------T------------------------------------------------,
I Nawe I Operation I Operand I
~----------+-~--------+------------------------------------------------i
I [syml:olJ I RDJFCB I ({dcb-addr, [(op
t
:l-code[,opt
2
-code])],} •.• ) I
L __________ ~ __________ ~ ________________________________________________ J
dcb, (opt:l I opt
2
)
(same as deb, Opt:ll and Opt2 operands in OPEN macro-instruction)
Although the opt:l and opt2 operands are not meaningful during the
execution of the RDJFCB macro-instruction, these oper~nds can
appear in the L-form of either the RDJFCB or OPEN macro-instruction
to generate identical parameter lists, which can be referred to
with the E-forw of either macro-instruction.
Examples: The macro-instruction in EX1 creates a parameter list for two
data control blocks: INVEN and MA'STER. In creating the list, both data
control blocks are assumed to be opened for input; opt2 for both blocks
is assumed to be DISP. The macro-instruction in EX2 reads the
system-created JFCBs for rUVEN and MASTER frcm the job queue into main
~torage, thus making the JFCB's available to the problem program for
mooification. The macro-instruction in EX3 modifies the parameter list
entry for the data control block namEd INVEN and indicates, through the
TYPE=J operand, -that the problem is supplying the JFCB's for system use.
System Macro-Instructions 131

IBM System/360 Specifications

General

Brand	IBM
Model	System/360
Category	Desktop
Language	English